html5doctor/diveintohtml5 — Issue #1: Serious error in introduction.html
Author: jribbens
Created: 2011-10-26 16:20:18+00:00
State: open

introduction.html has a significant error. It says "Upgrading to the HTML5 doctype won’t break your existing markup, because all the tags defined in HTML 4 are still supported in HTML5."

This is not true. There are many tags defined in HTML 4 that do not exist in HTML 5, e.g. , , , , , etc. There are also many attributes that have been removed, e.g. , ,

, etc.

I suspect that in reality, most HTML 4 documents will require significant changes to be valid HTML 5 documents - so advising people that they can simply replace their HTML 4 doctype with an HTML 5 doctype without otherwise changing the document itself is quite wrong.